The present invention relates to the ignition of gases that are combustible. More particularly, the present invention relates to an ignition assembly and the associated controls for the ignition of combustible gases resulting from the operation of chemical plants, refineries, pipelines, and oil field production units which produce combustible gases and which must be disposed of either continuously or intermittently through vertical or horizontal flare or vent pipes or stacks.
Many chemical plants, refineries, pipelines, loading docks, oilfield production units, off-shore drilling platforms, and other operations generate waste gases which must be disposed of through flaring and must be ignited so that the disposal is safe and effective. Often these waste gases are merely by-products of the process and are consistently produced in relatively constant volume. In other instances, because of upsets in plant operations, large quantities of gases such as feed materials, intermediates or products, must be disposed of quickly to prevent explosions or other hazardous conditions from occuring in the plant. Regardless of the source, however, the most commonly employed means of disposing of waste gases in the combustion thereof is generally by means of elevated flare stacks. The effectiveness and safety of this method of disposing of waste gases is dependent on igniting these gases either through a standing or intermittent pilot, or with a constant or intermittent electric ignition. Ignitor unit as used herein refers to that structure at the exit end of a flare or vent stack from which the waste gases pass and are ignited.
The present means of igniting waste gases at the end of a flare stack is with a constant burning pilot. Since a pilot uses natural gas or propane which is becoming more costly, a method of igniting either the pilot or a direct ignition of the flare gases by the use of an electrical ignitor is advantageous. The present method of ignition of a pilot at the top of a stack is mixing natural or propane gas and air at the ground level and igniting it and forcing this ignited gas up a long tube to a pilot at the top of the stack. This method, however, is not a positive method of ignition.
Other methods for igniting flare stack gases have been proposed and run the gamut from sending personnel up the stack to light the gas, to shooting fiery arrows across the top of the stack from ground level. It has been found, however, that these methods are at best ineffective and dangerous.
It has also been proposed to employ electrical means for igniting flare stack gases. However, electrical ignitors that have been used in the past have utilized single ignitor tips and have encountered the drawback in that severe shorting occurs in bad weather or with the build up of carbon material resulting from gas burning, with the result that no sparking occurs. Another with previous electric-type flare stack gas ignitors has been their inaccessible location. Thus, many have been mounted in a permanent fashion in order to render replacement difficult if not impossible, while others have been secured interiorly of the stack itself making repair and replacement hazardous.
These disadvantages of prior ignition methods are overcome with the present invention, and novel means and methods for electrically igniting the gas in a flare stack are herewith provided whereby an ignition spark across at least a pair of ignitor rods is provided and which may be controlled from ground level or from some remote site.